If you're talking about the intro for an essay:
You have to start strong with an attention grabber, or something that intrigues the readers such as a quote, personal connection, or statistic. Then you'll want to go with your background information and tell the reader the background for the essay you re about to write. For the last sentence of the paragraph, you make the two or three main points and you'll build your body paragraphs of those main points. Hope this helped!